Relates? to MC-125007.
Especially in cold biomes where everything exposed to the sky should be ice or snow, many decorations aren't being set properly. This happens around chunk boundaries (Subchunk bounds not tested yet)
Some trees are having snow generate under them.
some trees are cut off
lakes are spawning without snow/ice
This seems to encompass multiple bugs allegedly fixed in pre-10, from MC-132306 to MC-125007. I wonder if pre-10 just somehow didn't get released properly or if there was a lack of testing.
While the lack of activity since pre-10 together with the planned 1.13 release today is concerning, I hope Mojang reads this and other reinstantiated major world generation bugs and takes them serious BEFORE 1.13 goes out. It can't be stressed enough HOW important a working world generator is before an update that marks a major change in world generation to be followed by hopefully years of NOT messing with world generation anymore.
Everything else can be fixed in 1.13.1 next month. But a chunk that's generated is beyond future repair.